Autorotative enhancement system

ABSTRACT

Embodiments refer generally to systems and methods for providing autorotative enhancement for helicopters using an autorotative assist unit coupled to the transmission of the helicopter. Methods of utilizing an autorotative assist unit as well as retrofitting an autorotative assist unit to an existing helicopter are also disclosed. By employing an autorotative assist unit, improved autorotation can be achieved without the need to increase the weight of the rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and claims priority toU.S. patent application Ser. No. 14/934,477 filed on Nov. 6, 2015, nowU.S. Pat. No. 9,522,730, which is a continuation application of andclaims priority to U.S. patent application Ser. No. 13/834,215 filed onMar. 15, 2013, now U.S. Pat. No. 9,180,964. The entire contents of theforegoing patent applications are hereby incorporated by reference forall purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

In the event of engine failure, a helicopter can employ autorotation toexecute a safe landing, wherein the main rotor system of the helicopteris turned by the action of air moving up through the rotor. Thisgenerates lift and drag to slow the descent of the helicopter.Autorotation can allow the helicopter to descend and land safely withoutthe use of the main engine. Autorotation can be particularly useful forsingle engine helicopters.

SUMMARY

In some embodiments of the disclosure, an autorotative assist system fora rotor helicopter is disclosed as comprising a transmission coupled tothe rotor, an engine coupled to the transmission (via a drive shaft witha freewheeling unit allowing for free rotation of the rotor upon loss ofengine power), and an autorotative assist unit couple to thetransmission (typically independent of the engine primary drive system(e.g. drive shaft and/or free-wheeling unit) and/or without anyintervening component or gearing such as the freewheeling unit), whereinthe autorotative assist unit is operable to store energy during normalengine operation, and the autorotative assist unit is operable to drivethe rotor through the transmission to provide supplemental autorotativeassistance upon loss of engine power (e.g. when the engine rpm levelfalls below the rpm level of the rotor).

In other embodiments of the disclosure, a method of providingautorotative assistance for a rotor helicopter having an autorotativeassist unit is provided that comprises, upon loss of engine power,placing the helicopter into autorotation, and providing autorotativeassistance to the rotor from the autorotative assist unit (therebydriving the rotor as a supplement to autorotation).

In yet other embodiments of the disclosure, a method is disclosed forretrofitting a helicopter for improved autorotation capabilities,wherein the helicopter includes a rotor, a transmission having agenerator off the transmission housing, and an engine, the methodcomprising replacing the generator on the transmission with amotor-generator, providing a high capacity/high discharge rate batterysystem, and electrically connecting the motor-generator to the batterysystem so that, during normal engine operation, the motor-generatorcharges the battery system, but upon loss of engine power, themotor-generator is operable to draw energy from the battery system todrive the rotor for autorotative assistance.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description:

FIG. 1 illustrates a helicopter comprising an autorotative assist unitaccording to an embodiment of the disclosure;

FIG. 2A is a schematic illustration of an autorotative assist unitaccording to an embodiment of the disclosure;

FIG. 2B is a flowchart illustrating a method of providing autorotativeassistance for a rotor helicopter;

FIG. 3A is a side view of a system including the transmission, engineand rotor of a helicopter without an autorotative assist unit, shownwithin the helicopter;

FIG. 3B is a side view of a system including the transmission, engineand rotor of a helicopter without an autorotative assist unit;

FIG. 3C is a top view of a system including the transmission, engine androtor of a helicopter without an autorotative assist unit;

FIG. 3D is an perspective view of a system including the transmission,engine and rotor of a helicopter without an autorotative assist unit;

FIG. 4A is a side view of another system including the transmission,engine and rotor of a helicopter comprising an autorotative assist unit,shown within the helicopter;

FIG. 4B is a side view of a system including the transmission, engineand rotor of a helicopter comprising an autorotative assist unit;

FIG. 4C is a top view of a system including the transmission, engine androtor of a helicopter comprising an autorotative assist unit;

FIG. 4D is an perspective view of a system including the transmission,engine and rotor of a helicopter comprising an autorotative assist unit;

FIG. 4E is a flowchart illustrating a method of retrofitting ahelicopter for improved autorotation capabilities;

FIG. 5A is a side view of yet another system including the transmission,engine and rotor of a helicopter comprising an autorotative assist unit,shown within the helicopter;

FIG. 5B is a side view of a system including the transmission, engineand rotor of a helicopter comprising an autorotative assist unit;

FIG. 5C is a top view of a system including the transmission, engine androtor of a helicopter comprising an autorotative assist unit;

FIG. 5D is an perspective view of a system including the transmission,engine and rotor of a helicopter comprising an autorotative assist unit;and

FIG. 5E is a flowchart illustrating another method of retrofitting ahelicopter for improved autorotation capabilities.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods can be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but can bemodified within the scope of the appended claims along with their fullscope of equivalents.

In some cases, it can be desirable to provide enhancement or assistanceto the autorotation of a helicopter in the event of engine failure. Anautorotative assist unit can be operable to enhance the safety of thedescent and landing of a helicopter using autorotation. The autorotativeassist unit can provide supplemental power to the rotor system of ahelicopter during autorotation, such as a landing flare of energyoperable to slow descent of a helicopter right before landing, forexample. A landing flare can be used to execute a safe landing duringautorotation. Design criteria for helicopters can require the ability tocomplete autorotation from a certain density altitude, such as around7,000 feet, for example. To meet the criteria, an autorotative assistunit can be used to enhance the autorotative capabilities of thehelicopter.

Referring to FIG. 1, a system 100 according to an embodiment of thedisclosure is shown. The system 100 comprises a helicopter 120, whereinthe helicopter 120 comprises a fuselage 121, a transmission 102, anengine 104 mechanically coupled to the transmission 102, a rotor system108 mechanically coupled to the transmission 102, and an autorotativeassist unit 110 mechanically coupled to the transmission 102. The rotorsystem 108 can comprise a mast 107 coupled to the transmission 102 androtor blades 109 coupled to the mast 107. The transmission 102 can becoupled to the engine 104 via a drive shaft 105 and/or a freewheelingunit 106, wherein the freewheeling unit 106 allows for free rotation ofthe rotor 108 upon loss of power from the engine 104 (such can be neededto allow autorotation). The engine 104 can comprise a turbine or pistonengine, for example, and the helicopter 120 can be a single enginehelicopter or a multi-engine helicopter. In one embodiment, thehelicopter 120 can comprise a single engine helicopter with a rotor 108.The autorotative assist unit 110 is not typically used during normalengine operation (e.g. climb, cruise, hover, descent, etc.). Instead,the autorotative assist unit 110 can be operable to store energy (forexample, excess engine energy not required to drive the rotor 108)during normal engine operation. In the event of failure of the engine104, the freewheeling unit 106 can disengage the transmission 102 fromthe engine 104, and the autorotative assist unit 110 can be operable toprovide power to the transmission 102 and therefore the rotor 108 (as asupplement to normal autorotation). The autorotative assist unit can beapplicable to all rotor hub types, but it can be particularly helpful inhelicopters with articulated or low inertia rotors.

During autorotation, a pilot of the helicopter 120 can control theenergy output from the autorotative assist unit 110 to the rotor 108,for example, deciding when to use the supplemental power from theautorotative assist unit 110 and/or how much of the availableautorotative assist unit 110 power to use. The flight crew can beprovided with an indication of the amount of energy stored in theautorotative assist unit 110. For example, the output of energy can becontrolled automatically by the autorotative assist unit 110. In anotherexample, a “landing flare” of energy from the autorotative assist unit110 can be used to slow the descent of the helicopter 120 right beforelanding. In a further example, energy from the autorotative assist unit110 can be used to slow the helicopter 120 throughout the descent and/orat the landing. Additionally, the energy input from the autorotativeassist unit 110 can be used to stop descent, hover, level cruise, orpossibly lift the helicopter 120 if necessary (for example, to traversean obstacle). Several different methods can be used to input the energyfrom the autorotative assist unit 110 to the rotor 108 based on theconditions of the descent and landing and the abilities and decisions ofthe pilot of the helicopter 120.

In some embodiments, the autorotative assist unit 110 can respond tosensor input from sensors within the helicopter 120 to automaticallyprovide autorotative assistance. Sensors can provide informationcomprising engine revolutions per minute (rpm), rotor rpm, descent rate,and/or altitude, as well as energy stored in the autorotative assistunit 110. For example, the autorotative assist unit 110 can be triggeredto provide autorotative assistance when the rpm level of the engine 104falls below the rpm level of the rotor 108. Autorotative assistance canalso be controlled by a model or function executed by a controllercoupled to the autorotative assist unit 110.

In some embodiments, the autorotative assist unit 110 can comprise anelectric motor-generator, a battery system electrically coupled to themotor-generator operable to store and discharge energy, and a controlleroperable to control autorotative assist by communicating commands from apilot and/or receiving sensor data. In another embodiment, theautorotative assist unit 110 can comprise a hydraulic pump-motor, ahydraulic accumulator in fluid communication with the hydraulicpump-motor operable to store and discharge energy, and a controlleroperable to control release of the energy stored in the hydraulicaccumulator. In yet another embodiment, the autorotative assist unit 110can comprise a mechanical power storage system, such as a flywheel orspring arrangement, for example.

Referring now to FIG. 2A, a schematic illustration of an autorotativeassist system 200 is shown, according to an embodiment of thedisclosure. The autorotative assist system 200 can comprise atransmission 202, an engine 204 mechanically coupled to the transmission202 via a freewheeling unit 206, a rotor 208 mechanically coupled to thetransmission 202, and an autorotative assist unit 210 mechanicallycoupled to the transmission 202 (typically without any intermediategearing). In some embodiments, the autorotative assist unit 210 cancomprise a motor-generator 212 mechanically coupled to the transmission202, a battery system 214 electrically coupled to the motor-generator212, and a controller 216 for operating the motor-generator 212. In suchembodiments, the battery system 214 can comprise a high capacity/highdischarge rate battery system, such as a Lithium (Li) ion battery forexample. The battery system 214 can be operable to store energy duringnormal operation of the engine 204 and discharge this energy forautorotative assistance. By having a high discharge rate, the batterysystem 214 can allow for a boost of power for autorotative assistance. Ahigh capacity/high discharge rate battery system 214 can be operable torecover energy in a short period of time, which can enable repeatedautorotative assistance, such as can be used during a training exercise,for example.

The controller 216 can be operable to communicate commands to themotor-generator 212 for directing the stored power in the battery system214 of the autorotative assist unit 210 to power the motor-generator 212to drive the rotor 208. For example, the controller 216 can receivecommands from a pilot of the helicopter, for example. In anotherexample, the controller 216 can receive sensor input and, based on thesensor input, can automatically trigger the motor-generator 212 toprovide autorotative assistance. Additionally, a combination ofautomatic and manual control of the autorotative assist unit 210 can beprovided by the controller 216. In some embodiments, the energy input tothe rotor 208 can be spread out during the descent and/or the energy canbe used during the landing flare. This control of the energy output canbe scheduled by the controller 216, it can be triggered by a pilot, or acombination of the two can be used. For example, the autorotative assistunit 210 can automatically put the helicopter in an autorotative statewhen the engine 204 fails, and the energy remaining after doing so canbe used at the discretion of the pilot. In some embodiments, theautorotative assist unit 210 can be operable to provide about 80 hp forabout 6-7 seconds. In other embodiments, the autorotative assist unit210 can be operable to provide about 45 hp for about 3-4 seconds. In yetother embodiments, the autorotative assist unit 210 can be operable toprovide about 45-80 hp for about 3-7 seconds. In some embodiments, theautorotative assist unit 210 can weigh about 62-64 pounds. Typically,the weight of such an autorotative assist unit can be less than theadditional weight that would have to be added to the rotor to achieverotational inertia for comparable autorotation landing performance.

Some embodiments of the disclosure include methods 240, shown in FIG. 2Bof providing autorotative assistance for a rotor helicopter, wherein thehelicopter comprises an autorotative assist unit 210. The method 240 cancomprise, at block 244, placing the helicopter into autorotation uponloss of engine power. This can be done manually by the pilot orautomatically by controls in the helicopter. Then, when necessary, themethod 240 can comprise, at block 246, providing autorotative assistanceto the rotor 208 from the autorotative assist unit 210, thereby drivingthe rotor 208 as a supplement to autorotation. In some embodiments, themethod 240 can also comprise, at block 242, storing energy in theautorotative assist unit 210, such as in the battery system 214, duringnormal engine operation (wherein the storing energy can precede thesteps at blocks 244 and 246). Autorotative assistance can be triggeredmanually by pilot control and/or automatically based on sensor input,wherein the helicopter can comprise sensors operable to provideinformation to the autorotative assist unit 210, such as engine rpm,rotor rpm, speed, descent rate, and altitude, as well as energy storedin the battery system 214. In some embodiments, the autorotativeassistance comprises providing about 45-80 hp for about 3-7 seconds tothe rotor 208. Autorotative assistance can be provided at landing flareand/or during the descent of the helicopter (prior to landing flare) toslow the descent of the helicopter. In some embodiments, the method 240can further comprise, at block 248, after use of the autorotative assistunit 210, recharging the stored energy in the autorotative assist unit210 (such as in the battery system 214) after discharge. The step ofrecharging can be used in training for autorotation, for example.

Referring now to FIGS. 3A-3D, different views of a rotor drive system300 that does not comprise an autorotative assist unit are shown. Thetransmission 302 can be coupled to the rotor 308 (or mast of the rotorsystem) and to the engine 304 via a drive shaft 305 and a free-wheelingunit 306. The free-wheeling unit 306 can be operable to disengage theengine 304 from the transmission 302 upon engine failure to allow forautorotation. The transmission 302 can also be coupled to a hydraulicpump system 322 and an electric generator 324. The hydraulic pump system322 and electric generator 324 can couple to the transmission 302independently of the drive shaft 305 or the free-wheeling unit 306.

Referring now to FIGS. 4A-4D, a detailed view of a system 400 comprisingan electrically-based autorotative assist unit 410 is shown. Similarlyto the system 300 shown in FIGS. 3A-3D, the transmission 402 is coupledto the engine 404, via a drive shaft 405 and a free-wheeling unit 406,and to the rotor 408 (or mast of the rotor system). The transmission 402can also be coupled to a hydraulic pump system 422 and an autorotativeassist unit 410. The autorotative assist unit 410 can comprise amotor-generator 412, a battery system 414 and a controller 416. In someembodiments, the motor-generator 412 of the autorotative assist unit 410can take the place of an electric generator 324 (as shown in FIGS.3A-3D).

Some embodiments of the disclosure can include methods, as shown in FIG.4E of retrofitting a helicopter for improved autorotation capabilities,wherein the helicopter 420 comprises a rotor 408, a transmission 402having a generator 324 (as shown in FIGS. 3A-3D) off the transmissionhousing 402, and an engine 404. The method 440 can comprise, at block442, replacing the generator 324 on the transmission 402 with amotor-generator 412. Then, at block 444, the method can compriseproviding a high capacity/high discharge rate battery system 414,wherein, in some embodiments, the new battery system 414 can replace aportion of the battery system already existing in the helicopter 420.The method can then comprise, at block 446, electrically connecting themotor-generator 412 to the battery system 414 so that during normalengine operation, the motor-generator 412 charges the battery system414, but upon loss of engine power, the motor-generator 412 is operableto draw energy from the battery system 414 to drive the rotor 408 forautorotative assistance. Additionally, the transmission 402 can coupleto a free-wheeling unit 406, and the motor-generator 412 and the engine404 can be coupled to the transmission 402 on opposite sides of thefreewheeling unit 406. In other words, the motor-generator 412 can becoupled to the transmission 402 independently of a drive shaft 405(and/or free-wheeling unit 406) from the engine 404. Typically, themotor-generator 412 can be coupled to the transmission without anyintervening components, such as gearing. The method can additionallycomprise, at block 448, providing a controller 416, as well asoptionally one or more sensors in communication with the controller 416,for triggering the motor-generator 412 to draw energy from the batterysystem 414 to provide power to the rotor 408 during autorotation. Insome embodiments, the motor-generator 412 and battery system 414 can beoperable to provide about 45-80 hp to the rotor 408 for about 3-7seconds during autorotation. Additionally, the motor-generator 412 andbattery system 414 can weigh no more than about 65 pounds, for exampleabout 60-65 pounds, in some embodiments.

Referring now to FIGS. 5A-5D, a detailed view of a system 500 comprisinga hydraulically-based autorotative assist unit 510 is shown. Similarlyto the system 300 shown in FIGS. 3A-3D, the transmission 502 is coupledto the engine 504, via a drive shaft 505 and a free-wheeling unit 506,and to the rotor 508 (or mast of the rotor system). The transmission 502can also be coupled to an electric generator 524 and an autorotativeassist unit 510. The autorotative assist unit 510 can comprise ahydraulic pump-motor 512, a hydraulic accumulator 514 and a controller516. In some embodiments, hydraulic pump-motor 512 of the autorotativeassist unit 510 can take the place of a hydraulic pump system 322 (asshown in FIGS. 3A-3D). Although not specifically shown, it should beunderstood that the AAU in some embodiments can comprises bothelectrical and hydraulic features.

Some embodiments of the disclosure can include methods, shown in FIG.5E, of retrofitting a helicopter for improved autorotation capabilities,wherein the helicopter comprises a rotor 508, a transmission 502 havinga hydraulic pump 322 (as shown in FIGS. 3A-3D) off the transmissionhousing 502, and an engine 504. The method 540 can comprise, at block542, replacing the hydraulic pump 322 on the transmission 502 with ahydraulic pump-motor 512. Then, at block 544, the method can compriseproviding a hydraulic accumulator 514 in fluid communication with thehydraulic pump-motor 512, wherein during normal engine operation, thehydraulic pump-motor 512 pressurizes (e.g. stores hydraulic energy in)the hydraulic accumulator 514, but upon loss of engine power, thehydraulic pump-motor 512 draws pressure (energy) from the hydraulicaccumulator 514 to drive the rotor for autorotative assistance. In someembodiments, the hydraulic accumulator 514 can comprise a pressurevessel. Additionally, the transmission 502 can couple to a free-wheelingunit 506 and the hydraulic pump-motor 512 and the engine 504 can becoupled to the transmission 502 on opposite sides of the freewheelingunit 506. In other words, the hydraulic pump-motor 512 can be coupled tothe transmission 502 independently of a drive shaft 505 from the engine504. Typically, the pump-motor can be coupled to the transmissionwithout any intervening components, such as gearing. The method canadditionally comprise, at block 546, providing a controller 516, as wellas optionally one or more sensors in communication with the controller516, for triggering the hydraulic pump-motor 512 to draw energy from thehydraulic accumulator 514 to provide power to the rotor 508 duringautorotation. In some embodiments, the hydraulic pump-motor 512 andhydraulic accumulator 514 can be operable to provide about 45-80 hp tothe rotor 508 for about 3-7 seconds during autorotation. Additionally,the hydraulic pump-motor 512 and hydraulic accumulator 514 can weighless than about 65 pounds, for example about 60-65 pounds, in someembodiments.

As has been described above and shown in the figures, certainembodiments of the disclosure include a shim that is used to bond acomponent to a bearing. The shim can have an elastic modulus value thatis lower than an elastic modulus value of the component being bonded tothe bearing. In such a case, as torsional strain is applied to thecomponent, the shim absorbs a portion of the torsional strain. Thisreduces an amount of torsional strain experienced by an adhesive layer.Accordingly, since the amount of torsional strain in the adhesive layeris reduced, the adhesive layer can be less likely to fail duringoperation and can require less maintenance. Additionally, the use of ashim can be advantageous in that it can replace custom molded bearingsand components, which can have long lead times and be difficult toassemble and replace.

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R₁, and an upper limit,R_(u), is disclosed, any number falling within the range is specificallydisclosed. In particular, the following numbers within the range arespecifically disclosed: R=R₁+k*(R_(u)-R₁), wherein k is a variableranging from 1 percent to 100 percent with a 1 percent increment, i.e.,k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97percent, 98 percent, 99 percent, or 100 percent. Unless otherwisestated, the term “about” shall mean plus or minus 10 percent of thesubsequent value. Moreover, any numerical range defined by two R numbersas defined in the above is also specifically disclosed. Use of the term“optionally” with respect to any element of a claim means that theelement is required, or alternatively, the element is not required, bothalternatives being within the scope of the claim. Use of broader termssuch as comprises, includes, and having should be understood to providesupport for narrower terms such as consisting of, consisting essentiallyof, and comprised substantially of Accordingly, the scope of protectionis not limited by the description set out above but is defined by theclaims that follow, that scope including all equivalents of the subjectmatter of the claims. Each and every claim is incorporated as furtherdisclosure into the specification and the claims are embodiment(s) ofthe present invention.

What is claimed: 1-20. (canceled)
 21. An autorotative assist systemcomprising: a motor-generator configured to attach to a transmission ofan engine, the engine configured to rotate rotor blades connected to thetransmission; and an energy storage unit coupled to the motor-generator,wherein, during normal operation of the engine, the motor-generator isconfigured to convert energy from the transmission into electricalenergy, and the energy storage unit is configured to receive and storethe electrical energy, and wherein, upon loss of engine power, theenergy storage unit is configured to provide the stored energy to themotor-generator, and the motor-generator is configured to be powered bythe energy received from the energy storage unit to drive thetransmission to provide supplemental autorotative assistance to rotatethe rotor blades.
 22. The system of claim 21, wherein, during normaloperation, the motor-generator is configured to operate as a generatorto provide supplemental electric power to the transmission.
 23. Thesystem of claim 21, wherein the energy storage unit comprises a highcapacity/high discharge rate battery system.
 24. The system of claim 21,further comprising a controller connected to the motor-generator and theenergy storage unit, the controller configured to control thesupplemental autorotative assistance provided upon loss of engine power.25. The system of claim 21, wherein the motor-generator and batterysystem are configured to provide about 80 hp for about 6-7 seconds. 26.The system of claim 21, wherein the motor-generator and battery systemare operable to provide about 45 hp for about 3-4 seconds.
 27. Thesystem of claim 21, further comprising a hydraulic pump system connectedto transmission. 28-39. (canceled)
 40. The system of claim 27, whereinthe energy storage unit is further configured to direct the storedenergy to the hydraulic pump-motor to drive the rotor.
 41. Anautorotative assist system comprising: a motor-generator configured toattach to a transmission of an engine, the engine configured to rotaterotor blades connected to the transmission; and an energy storage unitcoupled to the motor-generator, wherein, upon loss of engine power ofthe engine driving the transmission to rotate rotor blades, the energystorage unit is configured to provide the stored energy to themotor-generator, and the motor-generator is configured to be powered bythe energy received from the energy storage unit to drive thetransmission to provide supplemental autorotative assistance to rotatethe rotor blades through the transmission by operating themotor-generator using the stored energy to drive the rotor blades. 42.The system of claim 41, wherein, during normal operation, themotor-generator is configured to operate as a generator to providesupplemental electric power to the transmission.
 43. The system of claim41, wherein the energy storage unit comprises a high capacity/highdischarge rate battery system.
 44. The system of claim 41, furthercomprising a controller connected to the motor-generator and the energystorage unit, the controller configured to control the supplementalautorotative assistance provided upon loss of engine power.
 45. Thesystem of claim 41, wherein the motor-generator and battery system areconfigured to provide about 80 hp for about 6-7 seconds.
 46. The systemof claim 41, wherein the motor-generator and battery system are operableto provide about 45 hp for about 3-4 seconds.
 47. The system of claim41, further comprising a hydraulic pump system connected totransmission.
 48. The system of claim 47, wherein the energy storageunit is further configured to direct the stored energy to the hydraulicpump-motor to drive the rotor.